/*      $NetBSD: rawfs.c,v 1.11 2009/10/21 23:12:09 snj Exp $   */

/*
 * Copyright (c) 1995 Gordon W. Ross
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Raw file system - for stream devices like tapes.
 * No random access, only sequential read allowed.
 * This exists only to allow upper level code to be
 * shielded from the fact that the device must be
 * read only with whole block position and size.
 */

#include <sys/param.h>
#include <lib/libsa/stand.h>
#include <rawfs.h>

extern int debug;

#define RAWFS_BSIZE     8192

/*
 * In-core open file.
 */
struct file {
        daddr_t         fs_nextblk;     /* block number to read next */
        daddr_t         fs_curblk;      /* block number currently in buffer */
        int             fs_len;         /* amount left in f_buf */
        char            *fs_ptr;        /* read pointer into f_buf */
        char            fs_buf[RAWFS_BSIZE];
};

static int rawfs_get_block(struct open_file *);

int rawfs_open(const char *path, struct open_file *f)
{
        struct file *fs;

        /*
         * The actual PROM driver has already been opened.
         * Just allocate the I/O buffer, etc.
         */
        fs = alloc(sizeof(struct file));
        fs->fs_nextblk = 0;
        fs->fs_curblk = -1;
        fs->fs_len = 0;
        fs->fs_ptr = fs->fs_buf;

        f->f_fsdata = fs;
        return 0;
}

int rawfs_close(struct open_file *f)
{
        struct file *fs;

        fs = (struct file *)f->f_fsdata;
        f->f_fsdata = NULL;

        if (fs != NULL)
                dealloc(fs, sizeof(*fs));

        return 0;
}

int rawfs_read(struct open_file *f, void *start, u_int size, u_int *resid)
{
        struct file *fs = (struct file *)f->f_fsdata;
        char *addr = start;
        int error = 0;
        size_t csize;

        while (size != 0) {

                if (fs->fs_len == 0)
                        if ((error = rawfs_get_block(f)) != 0)
                                break;

                if (fs->fs_len <= 0)
                        break;  /* EOF */

                csize = size;
                if (csize > fs->fs_len)
                        csize = fs->fs_len;

                memcpy(addr, fs->fs_ptr, csize);
                fs->fs_ptr += csize;
                fs->fs_len -= csize;
                addr += csize;
                size -= csize;
        }
        if (resid)
                *resid = size;

        if (error) {
                errno = error;
                error = -1;
        }

        return error;
}

int rawfs_write(struct open_file *f, void *start, size_t size, size_t *resid)
{

        errno = EROFS;
        return -1;
}

off_t rawfs_seek(struct open_file *f, off_t offset, int where)
{
        struct file *fs = (struct file *)f->f_fsdata;
        daddr_t curblk, targblk;
        off_t newoff;
        int err, idx;

        /*
         * We support a very minimal feature set for lseek(2); just
         * enough to allow loadfile() to work with the parameters
         * we pass to it on boot.
         *
         * In all cases, we can't seek back past the start of the
         * current block.
         */
        curblk = (fs->fs_curblk < 0) ? 0 : fs->fs_curblk;

        /*
         * Only support SEEK_SET and SEEK_CUR which result in offsets
         * which don't require seeking backwards.
         */
        switch (where) {
        case SEEK_SET:
                newoff = offset;
                break;

        case SEEK_CUR:
                if (fs->fs_curblk < 0)
                        newoff = 0;
                else {
                        newoff = fs->fs_curblk * RAWFS_BSIZE;
                        newoff += RAWFS_BSIZE - fs->fs_len;
                }
                newoff += offset;
                break;

        default:
                errno = EINVAL;
                return -1;
        }

        if (newoff < (curblk * RAWFS_BSIZE)) {
                errno = EINVAL;
                return -1;
        }

        targblk = newoff / RAWFS_BSIZE;

        /*
         * If necessary, skip blocks until we hit the required target
         */
        err = 0;
        while (fs->fs_curblk != targblk && (err = rawfs_get_block(f)) == 0)
                ;

        if (err) {
                errno = err;
                return -1;
        }

        /*
         * Update the index within the loaded block
         */
        idx = newoff % RAWFS_BSIZE;
        fs->fs_len = RAWFS_BSIZE - idx;
        fs->fs_ptr = &fs->fs_buf[idx];

        return newoff;
}

int rawfs_stat(struct open_file *f, struct stat *sb)
{

        errno = EFTYPE;
        return -1;
}


/*
 * Read a block from the underlying stream device
 * (In our case, a tape drive.)
 */
static int
rawfs_get_block(struct open_file *f)
{
        struct file *fs;
        int error;
        size_t len;

        fs = (struct file *)f->f_fsdata;
        fs->fs_ptr = fs->fs_buf;

        twiddle();
        error = f->f_dev->dv_strategy(f->f_devdata, F_READ,
            fs->fs_nextblk * (RAWFS_BSIZE / DEV_BSIZE),
            RAWFS_BSIZE, fs->fs_buf, &len);

        if (error == 0) {
                fs->fs_len = len;
                fs->fs_curblk = fs->fs_nextblk;
                fs->fs_nextblk += 1;
        } else {
                errno = error;
                error = -1;
        }

        return error;
}